This invention relates to testing of materials, particularly materials which are non-homogenous.
These materials are mixtures of two or more component materials, each of which has a very different electrical conductivity and dielectric constant. Materials so composed, because of their electrical properties, are often termed non-homogeneous. Some examples of these kinds of materials are explosives, which are composed of the explosive molecule with high dielectric constant and an inert filler such as sawdust which has a comparatively low dielectric constant; another example is the mixture of water and soil, which may appear uniform in consistency, yet water and soil have clearly different electrical characteristics.
Further examples are water and suspended solids or even marbleized meat where the component elements in this case are lean muscle tissue and fatty tissue.
There has been a long-standing need for a rapid non-destructive test of non-homogenous materials that will readily identify them or give their properties. Two immediate applications for such tests are in the field of letter bomb detection and in soil analysis.
With respect to security detection, the ability to package explosives in small envelopes, and send them through the mail has presented a long-standing security problem. With respect to soil analysis, there is a need for a rapid soil test in the field, which will give information regarding moisture content or mechanical properties.
It has been found that both of these materials have distinct conductive characteristics which are non-linear over given frequency ranges. This information can be used to identify and analyze such materials.